Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | Format for Non-PCM Audio and Data in an AES3 Serial Digital Audio Interface (formal name) Non-PCM AES3 (common name) |
| Description | Society of Motion Picture and Television Engineers (SMPTE) extensions to the AES3 interface that specify a method for transmitting AC-3 compressed audio (instead of the LPCM uncompressed audio specified in AES3) and other types of data. The SMPTE extensions permit the inclusion of, and picture-synchronize with, multichannel surround sound within the technical confines of existing television technology. AC-3 audio, also known as Dolby Digital, is used in theater systems, DVDs, and can be incorporated in MPEG-2 streams. The other types of data specified in the extensions include "null data" (to permit preamble sync codes to be inserted into the data stream) and time stamp data to support synchronization. Additional SMPTE specifications concern wrapping tracks in what they call the AES3 format in MXF. See the list of Format specifications below. The main thrust of AES3 concerns cabling and the physical interface between devices (see Notes below); this Web site is primarily devoted to formats pertaining to the storage of digital content bitstreams and to related file, wrapper, or bundling formats. |
| Production phase | Interface format that may be used at any point in a production life cycle. |
| Relationship to other formats | |
| [Based on] | AC-3, AC-3 Compressed Audio (Dolby Digital) |
| Used by | MXF_AES3, MXF File with AES3 Audio in Generic Container |
| Used by | MPEG-2_MP, MPEG-2, Main Profile |
| Used by | MPEG-2_SP, MPEG-2, Simple Profile |
| Used by | MPEG-2_MP, MPEG-2, 4:2:2 Profile |
| Used by | MXF_SDTI-CP, MXF File with SDTI-CP in Generic Container |
| LC experience or existing holdings | None |
| LC preference | Not determined, although there is a general preference for uncompressed or losslessly compressed audio; AC-3 is lossy compressed. |
| Disclosure | Open standard. Developed by the Society of Motion Picture and Television Engineers (SMPTE), using an Audio Engineering Society (AES) standard as the basis. |
| Documentation | Covered by a variety of SMPTE and AES documents; see Format specifications below. |
| Adoption | Appears to be widely adopted, apparently to the greatest degree for DVDs and MPEG-2 video streams; Comments welcome. |
| Licensing and patent claims | None on the interface specification; see also AC-3. |
| Transparency | The interface specification is transparent; see also AC-3. |
| Self-documentation | Not applicable. |
| External dependencies | The AES3 specification used as a basis covers wiring and cable connectors. |
| Technical protection considerations | None |
| Normal rendering | Good support. |
| Fidelity (support for high audio resolution) | See AC-3. |
| Support for multiple sound channels | See AC-3. |
| Support for downloadable or user-defined sounds, samples, and patches | Not applicable |
| Functionality beyond normal sound rendering | Capable of including data that supports synchronization with video picture streams. |
| Tag type | Value | Note |
| Filename Extension | Not applicable | In general, not applicable |
| Filename Extension | aes | Reported as an extension for raw data adhering to SMPTE specification 302M (Mapping of AES3 Data into an MPEG-2 Transport Stream) when saved as a file by Snell & Wilcox devices. |
| Internet Media Type | Not applicable | |
| Magic numbers | Not applicable |
| General | The main body of AES3 specifies signal transmission via a single shielded twisted wire pair. Annex D, however, discusses the carriage of AES3 signals on structured wiring, e.g., the "category 5" cables associated with computer network installations, a topic that receives extended treatment in AES47, which specifies the method of carrying multiple channels of audio in linear PCM or AES3 format across an asynchronous transfer mode (ATM) network. Elaborations on audio signal transfer are the topics of AES10-2003, AES Recommended Practice for Digital Audio Engineering &8221; Serial Multichannel Audio Digital Interface (MADI) (Revision of AES10-1991), and AES50-2005: AES standard for digital audio engineering &8221; High-resolution multi-channel audio interconnection. |
| History |
URLs
• Relevant Society of Motion Picture and Television Engineers standards are sold from http://www.smpte.org/smpte_store/standards/.
• SMPTE 302M-2002 Television - Mapping of AES3 Data into
MPEG-2 Transport Stream
• SMPTE 331M-2004. Television - Element and Metadata
Definitions for the SDTI-CP
• SMPTE 337M-2000. Television - Format for Non-PCM Audio and
Data in AES3 Serial Digital Audio Interface
• SMPTE 338M-2000. Television - Format for Non-PCM Audio and
Data in AES3 - Data Types
• SMPTE 339M-2004. Television - Format for Non-PCM Audio and
Data in AES3 - Generic Data Types
• SMPTE 340M-2000. Television - Format for Non-PCM Audio and
Data in AES3 - ATSC A/52 (AC-3) Data Type
• SMPTE 341M-2000. Television - Format for Non-PCM Audio and
Data in AES3 - Captioning Data Type
• SMPTE 369M-2002. Television - Type D-11 Data Stream and
AES3 Data Mapping over SDTI
• Relevant Audio Engineering Society standards (PDF and paper) are sold from http://www.aes.org/publications/standards/.
• AES3-2003. AES standard for digital audio — Digital input-output interfacing — Serial transmission format for two-channel linearly represented digital audio data.
• AES5-2003. AES recommended practice for professional digital audio — Preferred sampling frequencies for applications employing pulse-code modulation.
• Draft version of AES5-2003 (http://www.aes.org/standards/b_comments/drafts/draft-rev-aes5-20xx.pdf)
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URLs
• Wikipedia article on AES3 (http://en.wikipedia.org/wiki/AES/EBU)
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